1. Technical Field
The present disclosure relates generally to the field of data networking and telecommunications. More particularly, in one exemplary aspect, the present disclosure is directed to context based line coding.
2. Description of Related Technology
High-Definition Multimedia Interface (HDMI) is an exemplary digital display interface standard for connecting multimedia data sources to multimedia display devices. Existing HDMI devices generally support video data, audio data, control data, and optionally network connections. Historically, HDMI was developed to improve audio visual (A/V) interface capabilities while still supporting legacy interfaces (e.g., Digital Visual Interface (DVI)). However, legacy signaling standards were designed around assumptions that are no longer accurate for many consumer electronics. Specifically, aggressive device form factors (e.g., those which are very spatially compact, contain metal casings or other components, etc.) may experience link reliability issues which were heretofore unknown.
For example, HDMI uses Transition Minimized Differential Signaling (TMDS) to reduce electromagnetic interference (EMI), and assist in accurate clock recovery. TMDS maps eight (8) bit data to ten (10) bit symbols. The mapping reduces the likelihood of overshooting or undershooting signaling transitions which can contribute to bit errors. Additionally, TMDS ensures that the data has regular transitions, which is required for clock-data recovery. The mapping scheme of TMDS is simple enough to be handled entirely in link layer hardware i.e., without the assistance of higher layer software.
While TMDS could be considered a form of 8B/10B encoding, it is appreciated that as used within the relevant arts, the term “8B/10B” refers to a specific protocol developed by IBM (the IBM 8B/10B scheme was subject to patents which have since expired). According to the IBM 8B/10B scheme (as described within “A DC Balanced, Partitioned-Block, 8B/10B Transmission Code” to Widmer and Franaszek, incorporated herein by reference in its entirety), the five (5) least significant bits (LSB) of data are encoded into a six (6) bit group (the 5b/6b portion) and the three (3) most significant bits (MSB) are encoded into a 4-bit group (the 3b/4b portion). These code groups are concatenated together to form a 10-bit symbol. For clarity, as used hereinafter, the term “8B/10B” refers to the common usage (i.e., the IBM 8B/10B variant).
Due to certain business considerations, future versions of HDMI may substitute the existing TMDS scheme with the more common 8B/10B scheme. Unfortunately, in under certain conditions TMDS provides significant benefits and/or redundancies which 8B/10B does not provide. Accordingly, improved methods and apparatus for combining the benefits of 8B/10B and TMDS are needed. More generally, solutions are needed to select from various forms of line coding according to a contextual consideration.